According to the airline, federal agents have to screen passengers before they reboard another plane and TSA agents were not available at the time.

The airline says they made alternative transportation arrangements, but those took longer than expected.

A full statement from Sun Country Airlines can be read below:

As a result of very bad weather issues in the Dallas Texas area, we’d like to sincerely apologize to our customers for any inconvenience they experienced during their travels last night on Sun Country Airlines flight 505 from Minneapolis-St. Paul International Airport (MSP) to Dallas-Fort Worth International Airport (DFW). Unfortunately, inclement weather forced DFW to close. To ensure the safety of our passengers, the flight was rerouted to nearby Waco, Texas to wait out the weather and refuel. The US Department of Transportation (DOT) requires airlines to deplane passengers from any plane grounded for three hours, so we deplaned all passengers immediately prior to the three-hour mark. Because federal regulations also require airlines to screen passengers prior to re-boarding the aircraft, we could not re-board passengers after receiving clearance to return to DFW because TSA agents were not available to screen passengers. While we arranged alternative transportation for our customers and did our best to make our passengers comfortable, due to the late hour, the alternative transportation took longer than expected to arrive, and we are sorry that we could not get them to DFW sooner. We sincerely apologize to our customers for any inconveniences they experienced during their travels.